One Mexican entering the United States this week has not had to worry about evading the border patrol, dying of dehydration in the Arizona desert or being rounded up by a redneck rancher. President Vicente Fox arrives as an honoured guest for the first state visit of the Bush administration but he is as heavily laden as any of the thousands of would-be immigrants who try to cross the border illegally each day.

The Mexican president arrives carrying the baggage of national expectations and hopes: expectations that he will be able to legalise the situation of millions of Mexicans living in the US without proper papers, and hopes that he will forge an agreement that will make it easier for people to come north and find work without having to cross the border by night.

Fox's progressive foreign minister Jorge Castaneda, a former journalist and political commentator, visited the US earlier this summer. He told a gathering of mainly Latino union members that the Mexican government was going for "the whole enchilada" on immigration - hoping to legalise all illegal Mexicans in the US and set in place a policy that would end the running sore of deaths on the border.

Now it looks as though Mexico will be offered a mouthful of enchilada rather than the whole plate. In an article in yesterday's New York Times, President Fox wrote: "President Bush and I are committed to reaching an agreement that will be fair and humane - and realistic. We both realise that migration is not a problem to be dealt with but an opportunity to be seized. Migrant labour bolsters the American economy while migrant remittances fuel the Mexican economy."

This is certainly true. While the US GDP per capita stands at $33,900 (£23,300), the Mexican figure is $5,780 and the disparity between two neighbouring countries is always going to fuel immigration. But this week's meeting between the two presidents is going to have to come up with more than well-meaning words.

Both presidents have encouraged expectations and if they fail to deliver something tangible from this week's talks there will be strong feeling of disappointment and disillusionment.

It is worth remembering that this is very much about more than just the Mexicans and Americans. The US is a magnet for immigration across the world because of the plentiful supply of service industry and agricultural jobs that the established population no longer wishes to undertake.

It is for this reason that no less than 13% of the current work force is immigrant labour. When the last survey of illegal immigrants in the US was carried out less then five years ago, the figures showed that people from many countries besides Mexico were flocking across the borders. While there were an estimated 2.7m Mexicans without papers in the country, there were also an estimated 335,000 Salvadoreans, 165,000 Guatemalans, 120,000 Canadians, 105,000 Haitians and tens of thousands of Colombians, Jamaicans, Irish and Poles who had slipped in to the country one way or another and stayed. Border patrol officers tell of encountering every nationality from Iranian to Russian to Chinese stumbling through the desert.

This week's talks between Fox and Bush will be watched with interest by the estimated 7-11m people of various nationalities who make up the bulk of the undocumented population of the US. That's a lot of people waiting to see just what size of enchilada President Bush serves up at the state banquet.